Electrophotographic imaging processes employing 2,4-diamino-triazines as the electrically photosensitive particles



y 20, 3 L. WEINBERGER 3,445,227

ELECTROPHOTOGRAPHIC IMAGING PROCESSES EMPLOYING 2,4.DIAMINO'TRIAZINES AS THE ELECTRICALLY PHOTOSENSITIVE PARTICLES Filed April 2, 1965 INVENTOR. LESTER WEINBERGER A 7' TORNE )"S' United States Patent 3,445,227 ELECTROPHOTOGRAPHIC IMAGING PROCESSES EMPLOYING 2,4-DIAMINO-TRIAZINES AS THE ELECTRICALLY PHOTOSENSITIVE PARTICLES Lester Weinberger, Rochester, N.Y., assignor to Xerox Corporation, Rochester, N.Y., a corporation of New York Filed Apr. 2, 1965, Ser. No. 445,179

Int. Cl. G03g 7/00 U.S. CI. 96-15 20 Claims ABSTRACT OF THE DISCLOSURE Substituted 2,4diamino-triazines are used as electrically photosensitive pigment particles in photoelectrophoretic imaging and conventional xerographic processes.

This invention relates in general to imaging methods. More specifically, the invention concerns the use of electrically photosensitive pigments in electrophotographic imaging systems.

There has been recently developed an electrophoretic imaging system capable of producing color images which utilizes electrically photosensitive particles. This process is described in detail and claimed in copending applications Ser. Nos. 384,737, now U.S. Patent 3,384,565; 384,- 681, now abandoned in favor of Ser. No. 655,023, now U.S. Patent 3,384,566; and 384,680, now abandoned in favor of Ser. No. 518,041, now U.S. Patent 3,383,993, all filed July 23, 1964. In such an imaging system, variously colored light absorbing particles are suspended in a nOnconductive liquid carrier. The suspension is placed between electrodes, subjected to a potential difference and exposed to an image. As these steps are completed, selective particle migration takes place in image configuration, providing a visible image at one or both of the electrodes. An essential component of the system is the suspended particles which must be intensely colored particles which are photosensitive and which apparently undergo a net change in charge polarity upon exposure to activating radiation, through interaction with one of the electrodes. The images are produced in color because mixtures of two or more differently colored sets of particles which are each sensitive only to light of a specific wavelength or narrow range of wavelengths are used. Particles used in this system must both have intense pure colors and be highly photosensitive. The pigments of the prior art often lack the purity and brillance of color, the high degree of photosensivity, and/or the preferred correlation between the peak spectral response and peak photosensitivity, necessary for use in such a system.

Another imaging system which utilizes electrically photosensitive material is the xerographic process as originally described in U.S. Patent 2,297,691 to C. F. Carlson. Here, the photosensitive material must be an effective photoconductive insulator, i.e. must be capable of holding an electrostatic charge in the dark and dissipating the charge to a conductive substrate when exposed to light. In the fundamental process, a base sheet of relatively low electrical resistance such as metal, paper, etc., hav ing a photoconductive insulating surface coated thereon, is electrically charged in the dark. The charged coating is then exposed to a light image. The charges leak off rapidly to the base sheet in proportion to the intensity of light to which any given area is exposed, the charge being substantially retained in non-exposed areas, forming a latent electrostatic image. After exposure, the coating is contacted with electrostatic marking particles in the dark.

3,445,227 Patented May 20, 1969 These particles adhere to the areas where the electrostatic charge remains, forming a powder image corresponding to the electrostatic image. Where the base sheet is relatively inexpensive, such as paper, the image may be fixed directly thereto as by heat or solvent fusing. Alternatively, the powder image may be transferred to a sheet of material, such as paper and fixed thereon.

Many photosensitive materials useful in the xerographic process are known in the art, e.g., vitreous selenium, sulfur, anthracene, zinc oxide, and polyvinyl carbazole. While several of these different materials are in commercial use today, each has deficiencies in such areas as photographic speed, spectral response, durability, reusability and cost such that there is a continuing need for improved materials. A third class of electrophotographic imaging which utilizes electricallly photosensitive materials has recently been developed. This class consists of two systems of surface deformation imaging which are generally referred to as frost imaging and relief imaging. Frost imaging is described in detail in a publication entitled A Cyclic Xerographic Method Based on Frost Deformation by R. W. Gundlach and C. J. Claus, Journal of Photographic Science and Engineering, January-February edition, 1963. Relief imaging is described in detail in U.S. Patents 3,055,006; 3,163,872; and 3,113,179.

For use in frost imaging, for example, a plate may be made by overcoating a conductive substrate with a layer of a photoconductive insulating material, which is then overcoated with a thermoplastic material. Alternatively, the photoconductive material may be dispersed in particulate form in the thermoplastic material and the mixture coated directly over the conductive substrate. Typically, a uniform electrostatic charge is imposed on the plate surface, then the plate is exposed to a light-and-shadow image to be reproduced. The charge is dissipated in light struck areas but remains in unexposed areas. The plate is heated or treated with a solvent vapor until the electrostatic attraction forces of the charge pattern exceed the surface tension forces of the film. When this threshold condition is reached, a series of very small surface or Wrinkles are spontaneously formed on the film surface, the depth of the wrinkles in any particular area of film being dependent upon the intensity of charge in that area. This gives the image a frosted appearance. Other methods of frost and relief charging, exposing, and developing are described in the abovementioned publication and patents. Many of the presently known photoconductive materials have an excessively limited spectral response and low photographic speed, and thus, are incapable of producing optimum frost or relief images.

It is, therefore, an object of this invention to provide electrophotographic imaging processes which overcome the above-noted deficiencies.

It is another object of this invention to provide novel electrophoretic imaging processes.

It is another object of this invention to provide novel xerographic imaging processes.

It is still another object of this invention to provide novel surface deformation imaging processes.

It is still another object of this invention to provide novel electrophoretic imaging systems capable of reproducing color images.

It is still another object of this invention to provide novel frost imaging processes.

It is still another object of this invention to provide Xerographic plates having maximum spectral and photosensitive responses in ranges other than those of prior plates.

The foregoing objects and others are accomplished in accordance with this invention, fundametally, by providing novel processes utilizing compositions having the general formula:

in which R represents an aryl or alkaryl group, substituted or unsubstituted; with tWo similar or different aryl-amino or alkaryl-amino compounds.

The compositions produced by the above reaction have common characteristics of a brilliant yellow color; of

substantial insolubility in water and the common organic solvents e.g., benzene, toluene, acetone, carbontetrachloride, chloroform, alcohols, and aliphatic hydrocarbons; and of usually high photosensitive response.

Of the compositions within the general formula listed above, those in which R and R represent substituted or unsubstituted amino-anthraquinones and R represents a polynuclear aromatic radical are preferred for use in electrophoretic imaging processes since they have especially pure color and are most highly photosensitive. They have been found to give the most desirable combination of color qualities and photosensitivity. Optimum results have been obtained with 2,4-di(1'-anthraquinonyl-amino)- 6-(1"-pyrenyl)-s-triazine. However, since the shade or tone of the compositions in the spectral and photosensitive responses vary silightly depending upon the substitutent used, intermediate values of these variables may be obtained by mixing several of the compositions of this invention.

The compositions within the general formula listed above, and mixtures thereof, are especially useful as photosensitive pigment particles in electrophoretic imaging processes. An exemplary electrophoretic imaging system is shown in the figure.

Referring now to the figure, there is seen a transparent electrode generally designated 1 which, in this instance, is made up of a layer of optically transparent glass 2 overcoated with a thin optically transparent layer 3 of tin oxide, commercially available under the name NESA glass. This electrode shall hereafter be referred to as the injecting electrode. Coated on the surface of injecting electrode 1 is a thin layer 4 of [finely divided photosensitive particles dispersed in an insulating liquid carrier. The term photosensitive, for the purposes of this application, refers to the properties of a particle which, once attracted to the injecting electrode, will migrate away from it under the influence of an applied electric field when it is exposed to actinic electromagnetic radiation. For a detailed theoretical explanation of the apparent mechanism of operation of the invention, see the above-mentioned copending ap-.

plications, Ser. Nos. 384,737; 384,361; and 384,680, the disclosures of which are incorporated herein b reference. Liquid suspension 4 may also contain a sensitizer and/or a binder for the particles which is at least partially soluble in the suspen ing or carrier liquid, A j ent to he liq id suspension 4 is a second electrode 5, hereinafter called the blocking electrode, which is connected to one side of the potential source 6 through a switch 7. The opposite side of potential source 6 is connected to the injecting electrode .1 so that when switch 7 is closed, an electric field is applied across the liquid suspension 4 between electrodes 1 and 5. An image projector made up of a light source 8, a transparency 9, and a lens 10 is provided to expose the dispersion 4 to a light image of the original transparency 9 to be reproduced. Electrode 5 is made in the form of a roller having a conductive central core 11 connected to the potential source 6. The core is covered with a layer of a blocking electrode material 12, which may be Baryta paper. The particle suspension is exposed to the image to be reproduced while potential is applied across the blocking and injecting electrodes by closing switch 7. Roller 5 is caused to roll across the top surface of injecting electrode 1 with switch 7 closed during the period of image exposure. This light exposure causes exposed particles originally attracted to electrode 1 to migrate through the liquid and adhere to the surface of the blocking electrode, leaving behind an image on the injecting electrode surface which is a duplicate of the original transparency 9'. After exposure, the relatively volatile carrier liquid evaporates off, leaving behind the particulate image. This image may then be fixed in place as, for example, by placing a lamination over its top surface or a dissolved binder material in the carrier liquid such as parafiin wax or other suitable binder that comes out of solution as the carrier liquid evaporates. About 3% to 6% by weight of paraflin binder in the carrier has been found to produce good results. The carrier liquid itself may be paraffin wax or other suitable binder. In the alternative, the pigment image remaining on the injecting electrode may be transferred to another surface and fixed thereon. This system can produce either monochromatic or polychromatic images depending upon the type and number of different colored particles suspended in the carrier liquid and the color of light to which this suspension is exposed in the process.

Any suitable insulating liquid may be used as the carrier for the particles in the system. Typical carrier materials are decane, dodecane, N-tetradecane, paraffin, beeswax, or other thermoplastic materials, Sohio Odorless Solvent (a kerosene fraction available from Standard Oil Company of Ohio), and Isopar-G (a long chain satuarted aliphatic hydrocarbon available from Humble Oil Company of New Jersey). Good quality images have been produced with voltages ranging from 300 to 5,000 volts, in the apparatus of the figure.

In a monochromatic system, particles of a single color are dispersed in the carrier liquid and exposed to a black-and-white image. A single color image results, corresponding to a conventional black-and-white photography. In a polychromatic system, the particles are selected so that those of different colors respond to different wavelengths in the visible spectrum coresponding to their principal absorption bands. Also, the particles should be selected so that their spectral response curves do not have substantial overlap, thus allowing for good color separation and subtractive multicolor image formation. In a typical multicolor system, the particle dispersion should include cyan colored particles sensitive mainly to red light, magenta colored particles sensitive mainly to green light, and yellow colored particles sensitive mainly to blue light. When mixed together in a carrier liquid these particles produce a black appearing liquid. When one or more of the particles are caused to migrate from base electrode 11 toward an upper electrode, they leave behind particles which produce a color equivalent to the color of the impinging light. Thus, for example, red light exposure causes the cyan colored particles to migrate leaving behind the magenta and yellow particles which combine to produce red in the final image. In the same manner, blue and green colors are reproduced by removal of yellow and magenta respectively. When white light impinges upon the mix, all particles migrate leaving behind the color of the white or transparent substrate. No exposure leaves behind all particles which combine to produce a black image. This is an ideal technique of subtractive color imaging in that the particles are not only each composed of a single component but, in addition, they perform the dual functions of final image colorant and photosensitive medium.

It has been found that the compounds of the general formula given above are surprisingly effective when used in either a single or multicolor electrophoretic imaging system. Their good spectral response and high photosensitivity result in dense, brilliant images. It is known that in general, cyan and magenta particles separate from the tri-mix more easily and form more dense images than do the usual yellow particles. The yellow compositions herein disclosed, however, have surprisingly good color separation and image density characteristics.

Any suitable cyan and magenta colored photosensitive particles having the desired spectral responses may be used with the yellow particles of this invention to form a particle suspension in a carrier liquid for color imaging. From about 2 to about percent particles by weight have been found to produce good results. The addition of small amounts (generally ranging from 0.5 to 5 mole percent) of electron donors or acceptors to the suspensions may impart significant increases in system photosensitivity.

The following examples further specifically define the present invention with respect to the use of the compositions of the general formula given above in electrophoretic imaging processes. Parts and percentages are by weight unless otherwise indicated. The examples below are intended to illustrate various preferred embodiments of the electrophoretic imaging process of the present invention.

All of the following Examples I-XIV are carried out in an apparatus of the general type illustrated in the figure with the particle mix 4 coated on a NESA glass substrate through which exposure is made. The NESA glass surface is connected in series with a switch, a potential source, and the conductive center of a roller having a coating of Baryta paper on its surface. The roller is approximately 2% inches in diameter and is moved across the plate surface at about 1.45 centimeters per second. The plate employed is roughly 3 inches square and is exposed with a light intensity of 8,000 foot candles as measured on the uncoated NESA glass surface. Unless otherwise indicated, 7 percent by weight of the indicated pigments in each example are suspended in Sohio Odorless solvent 3440, a

kerosene fraction available from Standard Oil of Ohio, and the magnitude of the applied potential is 2,500 volts. All pigments which have a relatively large particle size as received commercially or as made are ground in a ball mill for 48 hours to reduce their size to provide a more stable dispersion which improves the resolution of the final images. The exposure is made with a 3200 K. lamp through a conventional positive black-and-white transparency.

Example I The suspension comprises about 7 parts 2,4 di-(1'- anthraquinonyl-amino)-6-(1"-pyrenyl)-s-triazine in about 100 parts Sohio Odorless Solvent 3440. This suspension, when exposed to a black-and-white image, produces a monochromatic image in yellow-and-White corresponding to the original.

Example II The suspension comprises about 7 parts of 2,4-di-(1'- anthraquinonyl-amino)-6-(1" naphthyl)-s-triazine. This suspension, when exposed to a black-and-white image, produces an excellent image corresponding to the original.

In each of the following examples, a suspension including equal amounts of three different colored pigments is made up by dispersing the pigments in finely divided form in Sohio Odorless Solvent 3440 so that the pigments constitute about 8 percent of the mixture. This mixture may be referred to as a tri-mix. The mixtures are individually tested by coating them on a NESA glass substrate and exposing them as in Example I above, except that a multicolor Kodachrome transparency is interposed between the light source and the plate instead of the black-andwhite transparency. Thus, a multicolored image is projected on the plate as the roller moves across the surface of the coated NESA glass substrate. A Baryta paper blocking electrode is employed and the roller is held at negative potential of about 2,500 volts with respect to the substrate. The roller is passed over the substrate six times, being cleaned after each pass. Potential application and exposure are both continued during the six passes by the roller. Then the quality of the image left on the substrate is evaluated as to density and color separation.

Example III The pigment mix consists of, as a magenta pigment, Watchung Red B, a barium salt of 1-(4-methyl-5'-chloro- 2'-sulfonic acid) azobenzene-Z-hydroxy-3-naphthoic acid, C.I. number 15865 available from Du Pont, as a cyan pig- :ment, Monolite Fast Blue GS, the alpha form of metalfree phthalocyanine, C.I. No. 74100, available from the Arnold Hoffman Company, and as a yellow pigment 2,4-di- 1-anthraquinonyl-amino)-6- 1"-pyrenyl) -s-triazine. This tri-mix, when exposed to a multi-colored image, produces a full color image with good density and color separation.

Example IV The pigment mixture consists of, as a magenta pigment, Locarno Red X-1686, C.I. No. 15865, 1-(4'-methyl- 5-chloro-2-sulfonic acid) azabenzene-Z-hydroxy-3-naphthoic acid, available from American Cyanamid, as a cyan pigment, Cyan Blue GTNF, the beta form of copper phthalocyanine, 01. No. 74160, available from Collway Colors, and as a yellow pigment 2,4-di-(1-naphthylamino)-6-( 1"-perylenyl)-s-triazine. This tri-mix is exposed to a multi-colored image and produces a full color image corresponding to the original.

Example V The pigment mixture consists of a magenta pigment, Naphtho Red B, 1-(2-methoxy5nitrophenylazo)-2-hydroxy-3"-nitro-3-naphthanilide, C.I. No. 12355, available from Collway Colors; a cyan pigment, a polychloro substituted copper phthalocyanine, C.I. No. 74260, available from Imperial Color and Chemical Company, and a yellow pigment 2,4(3'-cyano-anthraquinonyl-1'-amino)-6- (2"-cyano-1"-pyrenyl)-s-triazine. This tri-mix is exposed to a multi-color image and produces a full color image of good density and color separation.

Example VI The pigment mixture consinsts of a magenta pigment, Vulcan Fast Red BBE Toner 35-2201, 3,3'-dimethoxy- 4,4 biphenyl-bis(l-phenyl-3"methyl-4-azo- -perylene-5"-one), C.I. No. 21200, available from Collway Colors; a cyan pigment, Cyan Blue, 3,3'-methoxy-4,4'-diphenyl-bis(1"-azo-2"-hydroxy-3"-naphthanilide), C.I. No. 21180, available from Harmon Colors, and as a yellow pigment 2,4-di-(anthraquinonyl-1'-amino)-6-( l"-4"-ethylphenyl)-s-triazine. This tri-mix is exposed to a multicolored image and produces a full color image of good density and color separation.

Example VII The pigment suspension consists of a magenta pigment, Indofast Brilliant Scarlet Toner, 3,4,9,10-bis(N,N'-pmethoxyphenyl-imido)perylene, C.I. No. 71140, available from Harmon Colors; a cyan pigment, Monolite Fast Blue GS, the alpha form of metal-free phthalocyanine,

C.I. No. 74100, available from the Arnold Hoffman Company, and a yellow pigment, 2,4,6-tri- (1,1,1"- pyrenyl)-s-triazine. This tri-mix is exposed to a multicolored image and produces a full color image of satisfactory density and good color separation.

Examples VIII The pigment suspension consists of a magenta pigment Calcium Litho Red, the calcium lake of an azo dye, 1- (2'-azo-naphthalene-1-sulfonic acid)-2-hydroxy-naphtho, OJ. No. 15630, available from Collway Colors; a cyan pigment, Cyan Blue XR, the alpha form of copper phthalocyanine, available from Collway Colors, and a yellow pigment, 2,4-di-(3,8 dimethoxy-anthraquinonyl-l-ami no)-6-(l"-chrysenyl)-s-triazine. This tri-mix is exposed to a multi-colored image and produces a full color image of good density and color separation.

The novel compositions of the general formula given above are also useful in xerographic imaging systems. For use in such processes, xerographic plates may be produced by coating a relatively conductive substrate, e.g. aluminum or paper, with a dispersion of particles of the photosensitive pigment of the above general formula in a resin binder. The pigment-resin layer may also be cast as a self-supporting film. The plate formed may be both with or without an overcoating on the photoconductive layer. As a third alternative to the above-noted self-supporting layer and substrate supported layer, the photosensitive pigment-resin photoconductive layer may be used in the formation of multilayer sandwich configurations adjacent a dielectric layer, similar to that shown by Golovin et al., in the publication entitled, A New Electrophotographic Process, Effected by Means at Combined Electret Layers, Dodklady Akad. Nauk SSSR, vol. 129, No. 5, pp. 1 088 1011, November-December, 1959.

When it is desired to coate the pigmented resin film on a substrate various supporting materials may be used. Suitable materials for this purpose may include aluminum, steel, brass, metalized or tin oxide coated glass, semiconductive plastics and resins, paper and any other convenient material. Any suitable dielectric material may be used to overcoat the photoconductive layer. A typical overcoating is bichromated shellac.

Any suitable organic binder or resin may be used in combination with the pigment to prepare the photoconductive layer of this invention. In order to be useful the resin used in the present invention must be more resistive than about 10 and preferably more than 10 ohm/cm. under the conditions of xerographic use. Typical resins include thermoplastics such as polyvinylchloride, polyvinylacetates, polyvinylidenechloride, polystyrene, polybutadiene, polymethacrylates, polyacrylics, polyacrylonitrile, silicone resins, chlorinated rubber, and mixtures and copolymers thereof where applicable; and thermosetting resins such as epoxy resins including halogenated epoxy and phenoxy resins, phenolics, epoxy-phenolic copolymers, epoxy ureaformaldehyde copolymers, epoxy melamine formaldehyde copolymers and mixtures thereof where applicable. Other typical resins are epoxy esters, vinyl epoxy resins, tall-oil modified epoxies, and mixtures thereof where applicable. In addition to the above-noted materials any other suitable resin may be used, if desired. Also, other binders such as parafiin and mineral Waxes may be used, if desired.

The pigments may be incorporated in the dissolved or melted binder resin by any suitable means such as strong sheet agitation, preferably with simultaneous grinding. These include ball milling, roller milling, sand milling, ultrasonic agitation high-speed blending and any desirable combination of these methods. Any suitable range of pigment-resin ratios may be used.

The pigment-resin-solvent slurry (or the pigment-resin rnelt) may be applied to the conductive substrate by any of the well-known painting or coating methods, including spraying, flow coating, knife coating, C1CtrO'COalilI1g,

Mayer bar drawdown, dip coating, reverse roll coating, etc. Spraying in an electric field may be preferred for the smoothest finish and dip coating for convenience in the laboratory. The setting, drying and/or curing steps for these plates are generally similar to those recommended for films of the particular binder used for other painting applications. For example, pigment-epoxy plates may be cured by adding a cross-linking agent and stoving according to approximately the same schedule as other baking enamels made with the same resins and similar pigments for paint applications. A very desirable aspect of these pigments is that they are stable against chemical decomposition at the temperatures normally used for a wide variety of bake-on enamels and, therefore, may be incorporated in very hard glossy photoconductive coatings, similar to automotive or kitchen appliance resin finishes.

The thickness of the photoconductive films may be varied from about 1 to about 100 microns, depending on the required individual purpose. Self-supporting films, for example, cannot usually be manufactured in thicknesses thinner than about 10 microns, and they are easiest to handle and use in the 15 to micron range. Coatings, on the other hand, are preferably formed in the 5 to 30 micron range. For certain compositions and purposes, it is desirable to provide an overcoating; this should usually not exceed the thickness of the photoconductive coating, and preferably not about one-quarter of the latter. Any suitable overcoating material may be used such as bichromated shellac.

The invention as it pertains to xerographic imaging processes will be further described with reference to the following examples, which describe in detail various preferred embodiments of the present invention. Parts, ratios and percentages are by weight unless otherwise indicated. All the materials tested below were charged, exposed and developed according to conventional xerographic processes.

Xerographic plates for use as in the following examples are prepared as follows. Mixtures using specific pigments and resin binders are prepared by ball milling the pigment in a solution of a resinous binder and one or more solvents until the pigment is Well dispersed. This is done by adding the desired parts of the pigment to the desired parts of resin solution in a suitable mixing vessel. A quantity of one-eighth inch steel balls are added and the vessel is rotated for approximately one-half hour in order to obtain a homogeneous dispersion. The cooling slurry is applied onto an aluminum substrate with a wire drawdown rod and force dried in an oven for about 3 minutes at about 100 C. The coated sheets are dark rested for about one hour and then tested.

Example IX The xerographic plate is initially prepared by mixing about 10 parts Lucite 2042, an ethyl methacrylate polymer available from Du Pont, about parts benzene and about 2 parts 2,4-di-(1'-anthraquinonyl-amino)-6-(1"- pyrenyl)-s-triazine. The mixture is coated onto an aluminum substrate to a thickness of about 8 microns and cured. The plate is charged negative in the dark by means of a corona discharge to a potential of about 400 volts. The charged plate is exposed to a film positive for about 30 seconds by means of a high intensity, long wave, ultra-violet lamp (1680 microwatts/cm. of 3660 a.u. radiation at a distance of 18 inches). The latent electrostatic image is developed by cascading Xerox 1824 toner over the plate. The powder image on the plate is electrostatically transferred to a receiving sheet and heat fused. The image on the receiving sheet is of excellent quality and corresponds to the original. The plate is wiped clean of any residual toner and reused as in the above manner.

Example X A xerographic plate is prepared by initially mixing about 10 parts Lucite 2042, about 90 parts benzene and about 9 2 parts 2,4-di-(1'-anthraquinonyl-amino) 6 (1"perylenyl)-s-triazine. The mixture is coated onto an aluminum substrate to a thickness of about 8 microns and cured. The plate is charged, exposed and developed as in Example VIII above. The image produced is observed to be of good quality.

Example XI A xerographic plate is prepared by initially mixing about 10 parts Lucite 2042, about 90 parts benzene and about 2 parts 2,4,-di-(1'-anthraquinonyl-amino)-6-(1"-4" ethylphenyl)-s-triazine. The mixture is coated onto an aluminum substrate to a thickness of about 8 microns and cured. The plate is charged negative in the dark by means of a corona discharge to a potential of about 400 volts. The charge plate is exposed for about 45 seconds to a light-and-shadow image using a Simmons Omega D3 Enlarger equipped with a tungsten light source operating at 2950 K. color temperature. Illumination level incident on the plate is 2.8 foot candles as measured with a Weston Illumination Meter Model No. 756. The latent electrostatic image is then developed by cascading Xerox 1824 toner over the plate. The powder image on the plate is electrostatically transferred to a receiving sheet and heat fused. The image on the receiving sheet is of good quality and corresponds to the original. The plate is wiped clean of any residual toner and reused as in the above-described manner.

The third electrophotographic imaging process in which the above-listed novel photosensitive pigments are useful is that referred to as surface deformation imaging. As discussed above, this includes both frost and relief deformation of the surface of a deformable layer in image configuration.

Any suitable imaging method may be used in the surface deformation imaging processes of the present invention. The following methods are typical:

(1) The photoconductive thermoplastic layer is first substantially uniformly charged and exposed to a light and shadow image to be reproduced. The material is then heated until it deforms to form a frost pattern corresponding to the light and shadow image. The frost image thus formed is subsequently fixed or set by permitting the heat deformable layer to cool below its softening point. The image may be erased by reheating the layer in charge free condition to its softening point.

(2) In an alternative imaging process, the thermoplastic layer is uniformly charged and exposed to a light and shadow image. The material is then exposed to a solvent vapor, which softens the surface so that it deforms to form a frost pattern corresponding to the light and shadow image. Next, the solvent is removed by evaporation to fix or set the image. This image may be layer erased by resoftening the layer surface, by heat or additional solvent vapor.

(3) In still another alternative, a relief image may be formed by scanning the thermoplastic layer with an electron beam, either while the layer is softened, or just prior to heat or solvent softening. This image may be set by returning the layer to its pre-softened condition.

(4) Any of the methods described in detail in copending applications 193,277, 232,494, and 388,322 filed May 8, 1962, Oct. 23, 1962 and Aug. 7, 1964, respectively, may be used in the process of this invention. For example, the methods of forming the frost or relief image may vary depending upon the intended use of the resulting product. In certain situations, the heat deformable layer may be pretreated before uniformly charging the surface thereof. In addition, various suitable methods may be used to selectively fix and/or erase the material in imagewise configuration.

Any suitable material may be used as the surface deformable coating over the photoconductive layer or as the binder for the photosensitive pigments in a selfdeformable layer. Typical surface deformable thermoplastic polymers are low molecular weight polymers or oligomers. Any suitable polymer may be used in the surface deformation process of this invention; typical polymers are aromatic polymers such as polystyrene, alpha methylstyrene; copolymers made from styrene and other materials such as vinyl toluene, methyl-styrene, polyalphamethyl styrene, chlorinated styrene, and polymers and copolymers made from petroleum cuts and indene polymers; phenolics such as phenol aldehyde resins, phenol formaldehyde resins and mixtures thereof; vinyl polymers such as polyvinylacetate, polyvinylalcohol, polyvinylbutyral, butylmethyl-acrylate-styrene polymers, butylmethacrylate-alcoholated styrene copolymers, styrenemethacrylate-butadiene terpolymers; organo-polysiloxanes such as polydiphenylsiloxane; polyesters such as acrylic esters, bisphenol-A type polyesters; bisphenol-A copolymers; complex hydrocarbon polymers such as hydrogenated polyethylene and other mixtures and copolymers thereof. If desired, deformation characteristics of the films may be improved by incorporating on the surface thereof of thin surface skins as disclosed in copending application 388,323 filed Aug. 7, 1964.

The following examples will further specifically define the heat deformable imaging process of the present invention. Parts and percentages are by weight unless otherwise indicaated. The examples below are intended to illustrate various preferred embodiments of heat deformable imaging according to the present invention.

Broadly, the heat deformable image, either relief or frost may be formed either (1) by direct deformation of the thermoplastic binder containing the photosensitive pigment or (2) by overcoating the pigment-binder layer with a thermoplastic layer which is itself deforrnable.

Example XII A plate is prepared by initially mixing about 10 parts Lucite 2042, an ethyl methacrylate polymer available from Du Pont, about parts benzene and about 2 parts 2,4 di(1' anthraquinonyl-amino) 6 (1"-[2-cyano]- pyrenyl)-s-triazine. This mixture is coated onto an aluminum substrate to a thickness of about 8 microns and cured. The plate is then overcoated with about a 10 micron layer of Piccofiex -A (a polyvinylchloride resin obtained from Pennsylvania Industrial Chemicals Company). The composite plate is then charged to a negative potential of about 1,000 volts in the dark by means of a corona discharge. The charged plate is exposed through a film positive for about 30 seconds to a high intensity, long wave, ultra-violet lamp (1680 microwatts/cm. of 3660 an. radiation at a distance of 18 inches). The latent electrostatic image is then developed by placing the plate on a heated platen maintained at about 70 C. As the plate is heated to the softening point of the overcoating, a series of very small wrinkles or folds spontaneously forms in unexposed areas, giving the image a frosted appearance.

Example XIII A plate is prepared by initially mixing about 10 parts of Staybelite Ester No. 10, available from the Hercules Powder Co., about 90 parts benzene and about 2 parts 2,4 di ('1' anthl'aquinonyl-amino)-6-(1"-pyrenyl)-striazine. The mixture is coated onto an aluminum substrate to a thickness of about 10 microns and cured. The plate is charged negative in the dark by means of a corona discharge to a potential of about 1,000 volts. The charged plate is contact exposed to a film positive for about 30 seconds using a high intensity, long wave, ultraviolet lamp (1680 microwatts/cm. of 3660 an. radiation at a distance of 18 inches). The frost image is developed by placing the plate on a heated platen maintained at about 70 C. As the plate is heated to the softening point of the resin, frost again appears in image configuration.

11 Example XIV A xerographic plate is prepared by initially mixing about parts Lucite 2042, about 90 parts benzene and about 2 parts 2,4-di-(3',8-dimethoxy-anthraquinonyl-1'- amino)6-(1"-chrysenyl)-s-triazine. The mixture is coated onto an aluminum substrate to a thickness of about 8 microns and cured. The plate is then overcoated with about a 10 micron layer of Staybelite Ester No. 10. The composite plate is given an electrostatic charge, exposed, and heated to the softening point of the overcoating, as in Example XIII above. When this threshold point is reached, an excellent frost image appears.

Although specific components and proportions have been described in the above examples relating to electrophoretic, xerographic, and heat deformable imaging systems, other suitable materials, as listed above, may be used with similar results. In addition, other materials may be added to the pigment compositions or to the pigmentresin compositions to synergize, enhance or otherwise modify their properties. The pigment compositions and/ or the pigment-resin compositions of this invention may be dye sensitized, if desired, or may be mixed or other wise combined with other photoconductors, both organic and inorganic.

Other modifications and ramifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of this invention.

What is claimed is:

1. The method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between at least two electrodes, at least one of which is partially transparent, and simultaneously exposing said suspension to an image through said transparent electrode with activating electromagnetic radiation whereby a pigment image is formed on at least one of said electrodes; said suspension comprising a plurality of finely divided particles of at least one color, said particles of one color comprising a photosensitive pigment having the general formula:

R R and R are each selected from the group consisting of aryl, substituted aryl, alkaryl and substituted alkaryl.

2. The method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between at least two electrodes, at least one of which is partially transparent, and simultaneously exposing said suspension to an image through said transparent electrode with activating electromagnetic radiation whereby a pigment image is formed on at least one of said electrodes; said suspension comprising a plurality of finely divided particles of at least one color, said particles of one color comprising a photosensitive pigment having the general formula:

wherein:

R is a polynuclear aromatic radical; and

R and R are anthraquinone radicals.

3. The method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between at least two electrodes, at least one of which is partially transparent and simultaneously exposing said suspension to an image through said transparent electrode with activating electromagnetic radiation whereby a pigment image is formed on at least one of said electrodes; said suspension comprising a plurality of finely divided particles of at least one color, said particles of one color comprising as a photosensitive pigment 2,4-di- 1'-anthraquinonyl-amino)-6-(1"-pyrenyl) -s-triazine having the structure:

N N H l I! H rs 2 t H II 0 O 4. The method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between at least two electrodes, at least one of which is a blocking electrode, and simultaneously exposing said suspension to an image with activating electromagnetic radiation whereby a pigment image is formed on at least one of said electrodes; said suspension com prising a plurality of finely divided particles of at least one color, said particles of one color comprising a photosensitive pigment having the general formula:

N wherein:

R R and R are each selected from the group consisting of aryl, substituted aryl, alkaryl and substituted alkaryl.

5. The method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between at least two electrodes, at least one of which is a blocking electrode, and simultaneously exposing said suspension to an image with activating electromagnetic radiation whereby a pigment image is formed on at least one of said electrodes; said suspension comprising a plurality of finely divided particles of at least one color, said particles of one color comprising a photosensitive pigment having the general formula:

H N o N (ii l I Q N @Z: W o o 7. The method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between two electrodes, at least one of which is at least partly transparent, said suspension comprising a plurality of finely divided particles of at least two diflFerent colors in an insulating carrier liquid, the particles of each color comprising a photosensitive pigment whose principal light absorption band substantially coincides with its principal photosensitive response, simultaneously exposing said suspension to a light image through said partially transparent electrode and then separating said electrodes whereby a pigment image is formed on the surface of at least one of said electrodes, the particles of one color comprising compositions having the general formula:

N wherein:

R R and R are each selected from the group consisting of aryl, substituted aryl, alkaryl and substituted alkaryl.

8. The method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between two electrodes, at least one of which is at least partly transparent, said suspension comprising a plurality of finely divided particles of at least two ditferent colors in an insulating carrier liquid, the particles of each color comprising a photosensitive pigment whose principal' light absorption band substantially coincides with its principal photosensitive response, simultaneously exposing said suspension to a light image through said partially transparent electrode and then separating said electrodes whereby a pigment image is formed on the surface of at least one of said electrodes, the particles of one color comprising compositions having the general formula:

wherein:

R is a polynuclear aromatic radical; and, R and R are anthraquinone radicals.

9. The method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between two electrodes, at least one of which is at least partly transparent, said suspension comprising a plurality of finely divided particles of at least two different colors in an insulating carrier liquid, the particles of each color comprising a photosensitive pigment whose principal light absorption band substantially coincides with its principal photosensitive response, simultaneously exposing said suspension to a light image through said partially transparent electrode and then separating said electrodes whereby a pigment image is formed on the surface of at least one of said electrodes, the particles of one color comprising 2,4-di(l'-anthraquinonyl-amino) 6 (l-pyrenyl)-s-triazine having the structure:

10. The method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between two electrodes, at least one of which is a blocking electrode, said suspension comprising a plurality of finely divided particles of at least two different colors in an insulating carrier liquid, the particles of each color comprising a photosensitive pigment whose principal light absorption band substantially coincides with its principal photosensitive response, simultaneously exposing said suspension to a light image and then separating said electrodes whereby a pigment image is formed on the surface of at least one of said electrodes, the particles of one color comprising compositions having the general formula:

wherein:

R R and R are each selected from the group consisting of aryl, substituted aryl, alkaryl and substituted alkaryl.

11. The method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between two electrodes, at least one of which is a blocking electrode, said suspension comprising a plurality of finely divided particles of at least two difierent colors in an insulating carrier liquid, the particles of each color comprising a photosensitive pigment whose principal light absorption band substantially coincides with its principal photosensitive response, simultaneously exposing said suspension to a light image and then separating said electrodes whereby a pigment image is formed on the surface of at least one of said electrodes, the particles of one wherein:

R is a polynuclear aromatic radical; and,

R and R are anthraquinone radicals.

12. The method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between two electrodes, at least one of which is a blocking electrode, said suspension comprising a plurality of finely divided particles of at least two different colors in an insulating carrier liquid, the particles of each color comprising a photosensitive pigment whose principal light absorption band substantially coincides with its principal photosensitive response, simultaneously exposing said suspension to a light image and then separating said electrodes whereby a pigment image is formed on the surface of at least one of said electrodes, the particles of one color comprising 2,4 di (1-anthraquinonyl-amino)-6- -pyrenyl)-s-triazine having the structure:

wherein:

R R R are each selected from the group consisting of aryl, substituted aryl, alkaryl and substituted alkaryl.

14. A xerographic plate comprising a photoconductive layer comprising a binder material and a composition having the general formula:

wherein:

R is a polynuclear aromatic radical; and, R and R are anthraquinone radicals. 15. A Xerographic plate comprising a photoconductive 16 layer comprising a binder material and 2,4-di-(l'-anthraquinonylamino) 6 (1" pyrenyl) s triazine having the structure:

16. A process for forming a latent xerographie image on a photoconductive layer comprising a photoconductive pigment and an organic binder, which comprises electrostatically charging said layer and exposing said layer to a pattern of activating electromagnetic radiation; said photoconductive pigment comprising the composition having the general formula:

wherein:

R R and R are each selected from the group consisting of aryl, substituted aryl, alkaryl and substituted alkaryl.

17. A process for forming a latent xerographic image on a photoconductive layer comprising a photoconductive pigment and an organic binder, which comprises electrostatically charging said layer and exposing said layer to a pattern of activating electromagnetic radiation; said photoconductive pigment comprising the composition having the general formula:

wherein:

R is a polynuclear aromatic radical; and,

R and R are anthraquinone radicals.

1 8. A process for forming a latent xerographic image on a photoconductive layer comprising a photoconductive pigment and an organic binder, which comprises electrostatically charging said layer and exposing said layer to a pattern of activating electromagnetic radiation; said photoconductive pigment comprising 2,4-di-(1'-anthraquinonyl-amino) 6 (1" pyrenyl)-striazine having the structure:

N N H I I! H r to /C-N 19. A method for forming an image on a surface deformable recording medium which comprises electrostatically charging a recording medium, exposing said medium to a pattern of light-and-shadow and maintaining the surface of said medium in a sufliciently viscous condition to thereby deform at least a portion of said surface in a configuration corresponding to said pattern of lightand-shadow wherein said recording medium comprises photoconductive pigment particles in a thermoplastic binder, said photoconductive pigment comprising the composition having the general formula R1 N tilt Rr-NH( C-NEE-Rs wherein:

R R and R are each selected from the group con- 18 sisting of aryl, substituted aryl, alkaryl, and substituted alkaryl.

20. A method for forming an image on a surface deformable recording medium which comprises electrostatically charging a recording medium, exposing said medium to a pattern of light-and-shadow and maintaining the surface of said medium in a sufficiently viscous condition to thereby deform at least a portion of said surface in a configuration corresponding to said pattern of lightand-shadow, said recording medium comprising a coating of photoconductive pigment particles in an organic binder on a supporting substrate and an overcoat of thermoplastic material on said coating; said photoconductive pigment comprising the composition having the general formula:

wherein:

R R and R are each selected from the group consisting of aryl, substituted aryl, alkaryl, and substituted alkaryl.

References Cited UNITED STATES PATENTS 1,897,428 2/1933 Hentrich ct a1 260249.8 2,650,920 9/1953 Scalera et a1. 260249.8 2,832,779 4/1958 Ebel et al. 260249.8 3,130,046 4/1964 Schlesinger 961.5 3,238,041 3/1966 Corrsin 96-1.1 3,244,516 4/1966 Neugebauer et al 961.5 3,258,336 6/1966 Ewing 961.1

J. TRAVIS BROWN, Primary Examiner.

J. C. COOPER III, Assistant Examiner.

US. Cl. X.R. 96--1; 204-181 72 5 UNITED STATES PATENT OFFICE" CERTIFICATE OF CORRECTION Patent No. 4 2 a D t d May 20, 1969 Inventor s) Les ter Weinberger It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 41, after ..."surface"... insert -i'olds-. Column 3, line 3%, "usually" should read -unusually.

6km m0 smen APR 141970 Attest:

Ed t WILLIAM E. m.

Attestinz Officer f Goumissioner of Patents 

